The major aim of this proposal is to correlate the molecular structure with the functional properties of human histocompatibility antigens. Urine will be used as a source because of the strictures imposed by the complexity and small amounts of these antigens present in soluble extracts from lymphoid cells and in serum. In analogy with immunoglobulin research where rapid progress in protein structure was made once Bence-Jones proteins in the urine were utilized, the urine of patients with various neoplasias and non-malignant diseases as well as that of recipients of kidney transplants will be examined for increased amounts of excreted HLA antigens. Attempts will be made to increase the amounts of histocompatibility antigen in urine from normal subjects. Methods will be developed for the isolation of these antigens by combining classical physio-chemical purification procedures with immunochemical methods utilizing anti-Beta 2-microglobulin (Beta 2-Mu) and anti-HLA xenoantibodies coupled to immunoadsorbents. Efforts will be made to determine the molecular structure of the smallest fragment with antigenic activity and thus to elucidate the chemical composition of allotypic sites. The immunogenic properties of soluble, purified histocompatibility antigens will be evaluated by determining their ability to 1) elicit humoral responses in xenogeneic systems and 2) to effect in vitro cellular immune response in allogeneic systems. The data from these in vitro experiments will be correlated with the course of the neoplastic disease and with the outcome of kidney transplants. Since urine has been reported to contain tumor-associated antigens, the methodology developed in this study can be applied for the isolation and chemical characterization of neoplastic cell surface markers.